Yet, both constants \(C(\Vert g\Vert _{L^1})\)  and \(\delta \in (0,1)\)  where shown to exist but hard to calculate. These results provided a venue to obtain energy estimates suitable for the study of the evolution of \(L^r\) -norms for solutions to the Boltzmann equation later in [1]}, [2]}. Such initial results where limited to potentials satisfying certain regularity conditions in both kinetic and angular variables, including angular cut-off near \(\hat{u}\cdot \sigma =\pm 1\) .
